Circuit breakers may be used to protect an electrical circuit coupled to an electrical power supply. Circuit breakers may automatically interrupt power to the electrical circuit when, e.g., an overcurrent situation (i.e., excessive current) is detected. An overcurrent may result from, e.g., a short circuit, an overload, a ground fault, or the like. Automatic interruption of power is desired because it may prevent electrical shock hazards and/or damage to electrical equipment and surrounding infrastructure. Circuit breakers may also be manually operated to connect and disconnect power to and from an electrical circuit by throwing an operating handle pivotally mounted relative to the molded case of the circuit breaker. The operating handle typically has three configurations: ON, OFF, and TRIPPED. The ON position indicates that the main contacts of the circuit breaker are closed (i.e., in contact with each other), which connects power to the protected electrical circuit. The OFF configuration indicates that the main contacts have been opened manually via the operating handle to disconnect power from the electrical circuit. The TRIPPED configuration typically indicates that the main contacts have been opened automatically via a tripping mechanism in response to detection of an overcurrent, which disconnects power from the electrical circuit.
Under some abnormal operating conditions, the main contacts may become welded, fused, or otherwise stuck together. For example, a high in-rush current and/or a partial failure and/or a delay of the tripping mechanism may cause the main contacts to overheat to a point where they may melt and fuse together. This fused condition may go undetected. Consequently, a subsequent movement of the operating handle into the OFF configuration may not result in opening of the fused main contacts. This may erroneously indicate that power is disconnected from the protected electrical circuit when, in fact, power remains connected.
Accordingly, improved apparatus and methods that accommodate for such situations where the main contacts of the circuit breaker have become fused together are desired.